System and method for supporting SMA level abstractions at router ports for enablement of data traffic in a high performance computing environment

ABSTRACT

Systems and methods for supporting SMA level abstractions at router ports for enablement of data traffic in a high performance computing environment. In accordance with an embodiment, a subnet manager in a local subnet is responsible for enabling data traffic between subnets in a high performance computing environment. The SM can configure and set a data attribute at a switch port configured as a router port such that incoming data packets can be checked against the attribute to determine whether the data packet&#39;s destination is allowed or disallowed to receive inter-subnet data traffic.

CLAIM OF PRIORITY AND CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims the benefit ofpriority to, U.S. patent application entitled “SYSTEM AND METHOD FORSUPPORTING SMA LEVEL ABSTRACTIONS AT ROUTER PORTS FOR ENABLEMENT OF DATATRAFFIC IN A HIGH PERFORMANCE COMPUTING ENVIRONMENT”, application Ser.No. 15/414,277, filed on Jan. 24, 2017, which application claims thebenefit of priority to U.S. Provisional Patent Application entitled“SYSTEM AND METHOD FOR SUPPORTING ROUTER FEATURES IN A COMPUTINGENVIRONMENT”, Application No. 62/303,646, filed on Mar. 4, 2016, each ofwhich is incorporated by reference in its entirety.

This application is related to, and incorporates by reference in itsentirety, U.S. patent application entitled “SYSTEM AND METHOD FORSUPPORTING ROUTER SMA ABSTRACTIONS FOR SMP CONNECTIVITY CHECKS ACROSSVIRTUAL ROUTER PORTS IN A HIGH PERFORMANCE COMPUTING ENVIRONMENT”,application Ser. No. 15/413,149, filed on Jan. 23, 2017.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

FIELD OF INVENTION

The present invention is generally related to computer systems, and isparticularly related to supporting SMA level abstractions at routerports for enablement of data traffic in a high performance computingenvironment.

BACKGROUND

As larger cloud computing architectures are introduced, the performanceand administrative bottlenecks associated with the traditional networkand storage have become a significant problem. There has been anincreased interest in using high performance lossless interconnects suchas InfiniBand (IB) technology as the foundation for a cloud computingfabric. This is the general area that embodiments of the invention areintended to address.

SUMMARY

Described herein are methods and systems for supporting SMA levelabstractions at router ports for enablement of data traffic in a highperformance computing environment. A method can provide, at one or morecomputers, including one or more microprocessors, a first subnet, thefirst subnet comprising one or more switches, the one or more switchescomprising at least a leaf switch, wherein each of the one or moreswitches comprise a plurality of switch ports, a plurality of hostchannel adapters, each host channel adapter comprising at least one hostchannel adapter port, a plurality of end nodes, wherein each of the endnodes are associated with at least one host channel adapter of theplurality of host channel adapters, wherein each of the end nodes areassociated with a local identifier (LID) of a plurality of localidentifiers, and a subnet manager, the subnet manager running on one ofthe one or more switches and the plurality of host channel adapters. Amethod can configure a switch port of the plurality of switch ports on aswitch of the one or more switches as a router port. A method canlogically connect the switch port configured as the router port to avirtual router. The method can provide at the switch of the one or moreswitches that comprises the switch port of the plurality of switch portsconfigured as a router port a data attribute; wherein the data attributecomprises information about allowed and disallowed end nodes.

In accordance with an embodiment, one or more of the plurality of hostchannel adapters (either of the first or second subnet) can comprise atleast one virtual function, at least one virtual switch, and at leastone physical function. The plurality of end nodes (of the first orsecond subnet) can comprise physical hosts, virtual machines, or acombination of physical hosts and virtual machines, wherein the virtualmachines are associated with at least one virtual function.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an illustration of an InfiniBand environment, in accordancewith an embodiment.

FIG. 2 shows an illustration of a partitioned cluster environment, inaccordance with an embodiment

FIG. 3 shows an illustration of a tree topology in a networkenvironment, in accordance with an embodiment.

FIG. 4 shows an exemplary shared port architecture, in accordance withan embodiment.

FIG. 5 shows an exemplary vSwitch architecture, in accordance with anembodiment.

FIG. 6 shows an exemplary vPort architecture, in accordance with anembodiment.

FIG. 7 shows an exemplary vSwitch architecture with prepopulated LIDs,in accordance with an embodiment.

FIG. 8 shows an exemplary vSwitch architecture with dynamic LIDassignment, in accordance with an embodiment.

FIG. 9 shows an exemplary vSwitch architecture with vSwitch with dynamicLID assignment and prepopulated LIDs, in accordance with an embodiment.

FIG. 10 shows an exemplary multi-subnet InfiniBand fabric, in accordancewith an embodiment.

FIG. 11 shows an interconnection between two subnets in a highperformance computing environment, in accordance with an embodiment.

FIG. 12 shows an interconnection between two subnets via a dual-portvirtual router configuration in a high performance computingenvironment, in accordance with an embodiment.

FIG. 13 shows a flowchart of a method for supporting dual-port virtualrouter in a high performance computing environment, in accordance withan embodiment.

FIG. 14 is a flow chart illustrating a DR routed VSMP packet, inaccordance with an embodiment.

FIG. 15 is a flow chart illustrating a response to a DR routed VSMPpacket, in accordance with an embodiment.

FIG. 16 is a flow chart illustrating a LID routed VSMP packet, inaccordance with an embodiment.

FIG. 17 is a flow chart illustrating a response to a LID routed VSMPpacket, in accordance with an embodiment.

FIG. 18 illustrates a format for a Subnet Management Packet (SMP), inaccordance with an embodiment. More specifically, FIG. 18 shows an LIDrouted SMP packet.

FIG. 19 illustrates a common MAD header field, in accordance with anembodiment.

FIG. 20 shows a table of the subnet management attributes, and whichmethods can apply to each attribute, in accordance with an embodiment.

FIG. 21 illustrates a system for supporting SMA level abstractions atrouter ports for inter-subnet exchange of management information in ahigh performance computing environment, in accordance with anembodiment.

FIG. 22 is a flow chart of a method for supporting SMA levelabstractions at router ports for inter-subnet exchange of managementinformation in a high performance computing environment, in accordancewith an embodiment.

FIG. 23 depicts a trivial intermediate subnet, in accordance with anembodiment.

FIG. 24 is an illustration of a system for SMA abstraction for routerports for enablement of data traffic in a high performance computingenvironment, in accordance with an embodiment.

FIG. 25 depicts a flow chart of a method for supporting SMA levelabstractions at router ports for enablement of data traffic in a highperformance computing environment, in accordance with an embodiment.

DETAILED DESCRIPTION

The invention is illustrated, by way of example and not by way oflimitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” or “some” embodiment(s) in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone. While specific implementations are discussed, it is understood thatthe specific implementations are provided for illustrative purposesonly. A person skilled in the relevant art will recognize that othercomponents and configurations may be used without departing from thescope and spirit of the invention.

Common reference numerals can be used to indicate like elementsthroughout the drawings and detailed description; therefore, referencenumerals used in a figure may or may not be referenced in the detaileddescription specific to such figure if the element is describedelsewhere.

Described herein are systems methods for supporting SMA levelabstractions at router ports for enablement of data traffic in a highperformance computing environment.

The following description of the invention uses an InfiniBand™ (IB)network as an example for a high performance network. Throughout thefollowing description, reference can be made to the InfiniBand™specification (also referred to variously as the InfiniBandspecification, IB specification, or the legacy IB specification). Suchreference is understood to refer to the InfiniBand® Trade AssociationArchitecture Specification, Volume 1, Version 1.3, released March, 2015,available at http://www.inifinibandta.org, which is herein incorporatedby reference in its entirety. It will be apparent to those skilled inthe art that other types of high performance networks can be usedwithout limitation. The following description also uses the fat-treetopology as an example for a fabric topology. It will be apparent tothose skilled in the art that other types of fabric topologies can beused without limitation.

To meet the demands of the cloud in the current era (e.g., Exascaleera), it is desirable for virtual machines to be able to utilize lowoverhead network communication paradigms such as Remote Direct MemoryAccess (RDMA). RDMA bypasses the OS stack and communicates directly withthe hardware, thus, pass-through technology like Single-Root I/OVirtualization (SR-IOV) network adapters can be used. In accordance withan embodiment, a virtual switch (vSwitch) SR-IOV architecture can beprovided for applicability in high performance lossless interconnectionnetworks. As network reconfiguration time is critical to makelive-migration a practical option, in addition to network architecture,a scalable and topology-agnostic dynamic reconfiguration mechanism canbe provided.

In accordance with an embodiment, and furthermore, routing strategiesfor virtualized environments using vSwitches can be provided, and anefficient routing algorithm for network topologies (e.g., Fat-Treetopologies) can be provided. The dynamic reconfiguration mechanism canbe further tuned to minimize imposed overhead in Fat-Trees.

In accordance with an embodiment of the invention, virtualization can bebeneficial to efficient resource utilization and elastic resourceallocation in cloud computing. Live migration makes it possible tooptimize resource usage by moving virtual machines (VMs) betweenphysical servers in an application transparent manner. Thus,virtualization can enable consolidation, on-demand provisioning ofresources, and elasticity through live migration.

InfiniBand™

InfiniBand™ (IB) is an open standard lossless network technologydeveloped by the InfiniBand™ Trade Association. The technology is basedon a serial point-to-point full-duplex interconnect that offers highthroughput and low latency communication, geared particularly towardshigh-performance computing (HPC) applications and datacenters.

The InfiniBand™ Architecture (IBA) supports a two-layer topologicaldivision. At the lower layer, IB networks are referred to as subnets,where a subnet can include a set of hosts interconnected using switchesand point-to-point links. At the higher level, an IB fabric constitutesone or more subnets, which can be interconnected using routers.

Within a subnet, hosts can be connected using switches andpoint-to-point links. Additionally, there can be a master managemententity, the subnet manager (SM), which resides on a designated device inthe subnet. The subnet manager is responsible for configuring,activating and maintaining the IB subnet. Additionally, the subnetmanager (SM) can be responsible for performing routing tablecalculations in an IB fabric. Here, for example, the routing of the IBnetwork aims at proper load balancing between all source and destinationpairs in the local subnet.

Through the subnet management interface, the subnet manager exchangescontrol packets, which are referred to as subnet management packets(SMPs), with subnet management agents (SMAs). The subnet managementagents reside on every IB subnet device. By using SMPs, the subnetmanager is able to discover the fabric, configure end nodes andswitches, and receive notifications from SMAs.

In accordance with an embodiment, intra-subnet routing in an IB networkcan be based on linear forwarding tables (LFTs) stored in the switches.The LFTs are calculated by the SM according to the routing mechanism inuse. In a subnet, Host Channel Adapter (HCA) ports on the end nodes andswitches are addressed using local identifiers (LIDs). Each entry in alinear forwarding table (LFT) consists of a destination LID (DLID) andan output port. Only one entry per LID in the table is supported. When apacket arrives at a switch, its output port is determined by looking upthe DLID in the forwarding table of the switch. The routing isdeterministic as packets take the same path in the network between agiven source-destination pair (LID pair).

Generally, all other subnet managers, excepting the master subnetmanager, act in standby mode for fault-tolerance. In a situation where amaster subnet manager fails, however, a new master subnet manager isnegotiated by the standby subnet managers. The master subnet manageralso performs periodic sweeps of the subnet to detect any topologychanges and reconfigure the network accordingly.

Furthermore, hosts and switches within a subnet can be addressed usinglocal identifiers (LIDs), and a single subnet can be limited to 49151unicast LIDs. Besides the LIDs, which are the local addresses that arevalid within a subnet, each IB device can have a 64-bit global uniqueidentifier (GUID). A GUID can be used to form a global identifier (GID),which is an IB layer three (L3) address.

The SM can calculate routing tables (i.e., the connections/routesbetween each pair of nodes within the subnet) at network initializationtime. Furthermore, the routing tables can be updated whenever thetopology changes, in order to ensure connectivity and optimalperformance. During normal operations, the SM can perform periodic lightsweeps of the network to check for topology changes. If a change isdiscovered during a light sweep or if a message (trap) signaling anetwork change is received by the SM, the SM can reconfigure the networkaccording to the discovered changes.

For example, the SM can reconfigure the network when the networktopology changes, such as when a link goes down, when a device is added,or when a link is removed. The reconfiguration steps can include thesteps performed during the network initialization. Furthermore, thereconfigurations can have a local scope that is limited to the subnets,in which the network changes occurred. Also, the segmenting of a largefabric with routers may limit the reconfiguration scope.

An example InfiniBand fabric is shown in FIG. 1, which shows anillustration of an InfiniBand environment 100, in accordance with anembodiment. In the example shown in FIG. 1, nodes A-E, 101-105, use theInfiniBand fabric, 120, to communicate, via the respective host channeladapters 111-115. In accordance with an embodiment, the various nodes,e.g., nodes A-E, 101-105, can be represented by various physicaldevices. In accordance with an embodiment, the various nodes, e.g.,nodes A-E, 101-105, can be represented by various virtual devices, suchas virtual machines.

Partitioning in InfiniBand

In accordance with an embodiment, IB networks can support partitioningas a security mechanism to provide for isolation of logical groups ofsystems sharing a network fabric. Each HCA port on a node in the fabriccan be a member of one or more partitions. Partition memberships aremanaged by a centralized partition manager, which can be part of the SM.The SM can configure partition membership information on each port as atable of 16-bit partition keys (P_Keys). The SM can also configureswitch and router ports with the partition enforcement tables containingP_Key information associated with the end-nodes that send or receivedata traffic through these ports. Additionally, in a general case,partition membership of a switch port can represent a union of allmembership indirectly associated with LIDs routed via the port in anegress (towards the link) direction.

In accordance with an embodiment, partitions are logical groups of portssuch that the members of a group can only communicate to other membersof the same logical group. At host channel adapters (HCAs) and switches,packets can be filtered using the partition membership information toenforce isolation. Packets with invalid partitioning information can bedropped as soon as the packets reaches an incoming port. In partitionedIB systems, partitions can be used to create tenant clusters. Withpartition enforcement in place, a node cannot communicate with othernodes that belong to a different tenant cluster. In this way, thesecurity of the system can be guaranteed even in the presence ofcompromised or malicious tenant nodes.

In accordance with an embodiment, for the communication between nodes,Queue Pairs (QPs) and End-to-End contexts (EECs) can be assigned to aparticular partition, except for the management Queue Pairs (QP0 andQP1). The P_Key information can then be added to every IB transportpacket sent. When a packet arrives at an HCA port or a switch, its P_Keyvalue can be validated against a table configured by the SM. If aninvalid P_Key value is found, the packet is discarded immediately. Inthis way, communication is allowed only between ports sharing apartition.

An example of IB partitions is shown in FIG. 2, which shows anillustration of a partitioned cluster environment, in accordance with anembodiment. In the example shown in FIG. 2, nodes A-E, 101-105, use theInfiniBand fabric, 120, to communicate, via the respective host channeladapters 111-115. The nodes A-E are arranged into partitions, namelypartition 1, 130, partition 2, 140, and partition 3, 150. Partition 1comprises node A 101 and node D 104. Partition 2 comprises node A 101,node B 102, and node C 103. Partition 3 comprises node C 103 and node E105. Because of the arrangement of the partitions, node D 104 and node E105 are not allowed to communicate as these nodes do not share apartition. Meanwhile, for example, node A 101 and node C 103 are allowedto communicate as these nodes are both members of partition 2, 140.

Virtual Machines in InfiniBand

During the last decade, the prospect of virtualized High PerformanceComputing (HPC) environments has improved considerably as CPU overheadhas been practically removed through hardware virtualization support;memory overhead has been significantly reduced by virtualizing theMemory Management Unit; storage overhead has been reduced by the use offast SAN storages or distributed networked file systems; and network I/Ooverhead has been reduced by the use of device passthrough techniqueslike Single Root Input/Output Virtualization (SR-IOV). It is nowpossible for clouds to accommodate virtual HPC (vHPC) clusters usinghigh performance interconnect solutions and deliver the necessaryperformance.

However, when coupled with lossless networks, such as InfiniBand (IB),certain cloud functionality, such as live migration of virtual machines(VMs), still remains an issue due to the complicated addressing androuting schemes used in these solutions. IB is an interconnectionnetwork technology offering high bandwidth and low latency, thus, isvery well suited for HPC and other communication intensive workloads.

The traditional approach for connecting IB devices to VMs is byutilizing SR-IOV with direct assignment. However, achieving livemigration of VMs assigned with IB Host Channel Adapters (HCAs) usingSR-IOV has proved to be challenging. Each IB connected node has threedifferent addresses: LID, GUID, and GID. When a live migration happens,one or more of these addresses change. Other nodes communicating withthe VM-in-migration can lose connectivity. When this happens, the lostconnection can be attempted to be renewed by locating the virtualmachine's new address to reconnect to by sending Subnet Administration(SA) path record queries to the IB Subnet Manager (SM).

IB uses three different types of addresses. A first type of address isthe 16 bits Local Identifier (LID). At least one unique LID is assignedto each HCA port and each switch by the SM. The LIDs are used to routetraffic within a subnet. Since the LID is 16 bits long, 65536 uniqueaddress combinations can be made, of which only 49151 (0x0001-0xBFFF)can be used as unicast addresses. Consequently, the number of availableunicast addresses defines the maximum size of an IB subnet. A secondtype of address is the 64 bits Global Unique Identifier (GUID) assignedby the manufacturer to each device (e.g. HCAs and switches) and each HCAport. The SM may assign additional subnet unique GUIDs to an HCA port,which is useful when SR-IOV is used. A third type of address is the 128bits Global Identifier (GID). The GID is a valid IPv6 unicast address,and at least one is assigned to each HCA port. The GID is formed bycombining a globally unique 64 bits prefix assigned by the fabricadministrator, and the GUID address of each HCA port.

Fat-Tree (FTree) Topologies and Routing

In accordance with an embodiment, some of the IB based HPC systemsemploy a fat-tree topology to take advantage of the useful propertiesfat-trees offer. These properties include full bisection-bandwidth andinherent fault-tolerance due to the availability of multiple pathsbetween each source destination pair. The initial idea behind fat-treeswas to employ fatter links between nodes, with more available bandwidth,as the tree moves towards the roots of the topology. The fatter linkscan help to avoid congestion in the upper-level switches and thebisection-bandwidth is maintained.

FIG. 3 shows an illustration of a tree topology in a networkenvironment, in accordance with an embodiment. As shown in FIG. 3, oneor more end nodes 201-204 can be connected in a network fabric 200. Thenetwork fabric 200 can be based on a fat-tree topology, which includes aplurality of leaf switches 211-214, and multiple spine switches or rootswitches 231-234. Additionally, the network fabric 200 can include oneor more intermediate switches, such as switches 221-224.

Also as shown in FIG. 3, each of the end nodes 201-204 can be amulti-homed node, i.e., a single node that is connected to two or moreparts of the network fabric 200 through multiple ports. For example, thenode 201 can include the ports H1 and H2, the node 202 can include theports H3 and H4, the node 203 can include the ports H5 and H6, and thenode 204 can include the ports H7 and H8.

Additionally, each switch can have multiple switch ports. For example,the root switch 231 can have the switch ports 1-2, the root switch 232can have the switch ports 3-4, the root switch 233 can have the switchports 5-6, and the root switch 234 can have the switch ports 7-8.

In accordance with an embodiment, the fat-tree routing mechanism is oneof the most popular routing algorithm for IB based fat-tree topologies.The fat-tree routing mechanism is also implemented in the OFED (OpenFabric Enterprise Distribution—a standard software stack for buildingand deploying IB based applications) subnet manager, OpenSM.

The fat-tree routing mechanism aims to generate LFTs that evenly spreadshortest-path routes across the links in the network fabric. Themechanism traverses the fabric in the indexing order and assigns targetLIDs of the end nodes, and thus the corresponding routes, to each switchport. For the end nodes connected to the same leaf switch, the indexingorder can depend on the switch port to which the end node is connected(i.e., port numbering sequence). For each port, the mechanism canmaintain a port usage counter, and can use this port usage counter toselect a least-used port each time a new route is added.

In accordance with an embodiment, in a partitioned subnet, nodes thatare not members of a common partition are not allowed to communicate.Practically, this means that some of the routes assigned by the fat-treerouting algorithm are not used for the user traffic. The problem ariseswhen the fat tree routing mechanism generates LFTs for those routes thesame way it does for the other functional paths. This behavior canresult in degraded balancing on the links, as nodes are routed in theorder of indexing. As routing can be performed oblivious to thepartitions, fat-tree routed subnets, in general, provide poor isolationamong partitions.

In accordance with an embodiment, a Fat-Tree is a hierarchical networktopology that can scale with the available network resources. Moreover,Fat-Trees are easy to build using commodity switches placed on differentlevels of the hierarchy. Different variations of Fat-Trees are commonlyavailable, including k-ary-n-trees, Extended Generalized Fat-Trees(XGFTs), Parallel Ports Generalized Fat-Trees (PGFTs) and Real LifeFat-Trees (RLFTs).

A k-ary-n-tree is an n level Fat-Tree with k^(n) end nodes and n·k^(n-1)switches, each with 2 k ports. Each switch has an equal number of up anddown connections in the tree. XGFT Fat-Tree extends k-ary-n-trees byallowing both different number of up and down connections for theswitches, and different number of connections at each level in the tree.The PGFT definition further broadens the XGFT topologies and permitsmultiple connections between switches. A large variety of topologies canbe defined using XGFTs and PGFTs. However, for practical purposes, RLFT,which is a restricted version of PGFT, is introduced to define Fat-Treescommonly found in today's HPC clusters. An RLFT uses the same port-countswitches at all levels in the Fat-Tree.

Input/Output (I/O) virtualization

In accordance with an embodiment, I/O Virtualization (IOV) can provideavailability of I/O by allowing virtual machines (VMs) to access theunderlying physical resources. The combination of storage traffic andinter-server communication impose an increased load that may overwhelmthe I/O resources of a single server, leading to backlogs and idleprocessors as they are waiting for data. With the increase in number ofI/O requests, IOV can provide availability; and can improve performance,scalability and flexibility of the (virtualized) I/O resources to matchthe level of performance seen in modern CPU virtualization.

In accordance with an embodiment, IOV is desired as it can allow sharingof I/O resources and provide protected access to the resources from theVMs. IOV decouples a logical device, which is exposed to a VM, from itsphysical implementation. Currently, there can be different types of IOVtechnologies, such as emulation, paravirtualization, direct assignment(DA), and single root-I/O virtualization (SR-IOV).

In accordance with an embodiment, one type of IOV technology is softwareemulation. Software emulation can allow for a decoupledfront-end/back-end software architecture. The front-end can be a devicedriver placed in the VM, communicating with the back-end implemented bya hypervisor to provide I/O access. The physical device sharing ratio ishigh and live migrations of VMs are possible with just a fewmilliseconds of network downtime. However, software emulation introducesadditional, undesired computational overhead.

In accordance with an embodiment, another type of IOV technology isdirect device assignment. Direct device assignment involves a couplingof I/O devices to VMs, with no device sharing between VMs. Directassignment, or device passthrough, provides near to native performancewith minimum overhead. The physical device bypasses the hypervisor andis directly attached to the VM. However, a downside of such directdevice assignment is limited scalability, as there is no sharing amongvirtual machines—one physical network card is coupled with one VM.

In accordance with an embodiment, Single Root IOV (SR-IOV) can allow aphysical device to appear through hardware virtualization as multipleindependent lightweight instances of the same device. These instancescan be assigned to VMs as passthrough devices, and accessed as VirtualFunctions (VFs). The hypervisor accesses the device through a unique(per device), fully featured Physical Function (PF). SR-IOV eases thescalability issue of pure direct assignment. However, a problempresented by SR-IOV is that it can impair VM migration. Among these IOVtechnologies, SR-IOV can extend the PCI Express (PCIe) specificationwith the means to allow direct access to a single physical device frommultiple VMs while maintaining near to native performance. Thus, SR-IOVcan provide good performance and scalability.

SR-IOV allows a PCIe device to expose multiple virtual devices that canbe shared between multiple guests by allocating one virtual device toeach guest. Each SR-IOV device has at least one physical function (PF)and one or more associated virtual functions (VF). A PF is a normal PCIefunction controlled by the virtual machine monitor (VMM), or hypervisor,whereas a VF is a light-weight PCIe function. Each VF has its own baseaddress (BAR) and is assigned with a unique requester ID that enablesI/O memory management unit (IOMMU) to differentiate between the trafficstreams to/from different VFs. The IOMMU also apply memory and interrupttranslations between the PF and the VFs.

Unfortunately, however, direct device assignment techniques pose abarrier for cloud providers in situations where transparent livemigration of virtual machines is desired for data center optimization.The essence of live migration is that the memory contents of a VM arecopied to a remote hypervisor. Then the VM is paused at the sourcehypervisor, and the VM's operation is resumed at the destination. Whenusing software emulation methods, the network interfaces are virtual sotheir internal states are stored into the memory and get copied as well.Thus the downtime could be brought down to a few milliseconds.

However, migration becomes more difficult when direct device assignmenttechniques, such as SR-IOV, are used. In such situations, a completeinternal state of the network interface cannot be copied as it is tiedto the hardware. The SR-IOV VFs assigned to a VM are instead detached,the live migration will run, and a new VF will be attached at thedestination. In the case of InfiniBand and SR-IOV, this process canintroduce downtime in the order of seconds. Moreover, in an SR-IOVshared port model the addresses of the VM will change after themigration, causing additional overhead in the SM and a negative impacton the performance of the underlying network fabric.

InfiniBand SR-IOV Architecture—Shared Port

There can be different types of SR-IOV models, e.g. a shared port model,a virtual switch model, and a virtual port model.

FIG. 4 shows an exemplary shared port architecture, in accordance withan embodiment. As depicted in the figure, a host 300 (e.g., a hostchannel adapter) can interact with a hypervisor 310, which can assignthe various virtual functions 330, 340, 350, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 310.

In accordance with an embodiment, when using a shared port architecture,such as that depicted in FIG. 4, the host, e.g., HCA, appears as asingle port in the network with a single shared LID and shared QueuePair (QP) space between the physical function 320 and the virtualfunctions 330, 350, 350. However, each function (i.e., physical functionand virtual functions) can have their own GID.

As shown in FIG. 4, in accordance with an embodiment, different GIDs canbe assigned to the virtual functions and the physical function, and thespecial queue pairs, QP0 and QP1 (i.e., special purpose queue pairs thatare used for InfiniBand management packets), are owned by the physicalfunction. These QPs are exposed to the VFs as well, but the VFs are notallowed to use QP0 (all SMPs coming from VFs towards QP0 are discarded),and QP1 can act as a proxy of the actual QP1 owned by the PF.

In accordance with an embodiment, the shared port architecture can allowfor highly scalable data centers that are not limited by the number ofVMs (which attach to the network by being assigned to the virtualfunctions), as the LID space is only consumed by physical machines andswitches in the network.

However, a shortcoming of the shared port architecture is the inabilityto provide transparent live migration, hindering the potential forflexible VM placement. As each LID is associated with a specifichypervisor, and shared among all VMs residing on the hypervisor, amigrating VM (i.e., a virtual machine migrating to a destinationhypervisor) has to have its LID changed to the LID of the destinationhypervisor. Furthermore, as a consequence of the restricted QP0 access,a subnet manager cannot run inside a VM.

InfiniBand SR-IOV Architecture Models—Virtual Switch (vSwitch)

FIG. 5 shows an exemplary vSwitch architecture, in accordance with anembodiment. As depicted in the figure, a host 400 (e.g., a host channeladapter) can interact with a hypervisor 410, which can assign thevarious virtual functions 430, 440, 450, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 410. A virtual switch 415 can also be handled by thehypervisor 401.

In accordance with an embodiment, in a vSwitch architecture each virtualfunction 430, 440, 450 is a complete virtual Host Channel Adapter(vHCA), meaning that the VM assigned to a VF is assigned a complete setof IB addresses (e.g., GID, GUID, LID) and a dedicated QP space in thehardware. For the rest of the network and the SM, the HCA 400 looks likea switch, via the virtual switch 415, with additional nodes connected toit. The hypervisor 410 can use the PF 420, and the VMs (attached to thevirtual functions) use the VFs.

In accordance with an embodiment, a vSwitch architecture providetransparent virtualization. However, because each virtual function isassigned a unique LID, the number of available LIDs gets consumedrapidly. As well, with many LID addresses in use (i.e., one each foreach physical function and each virtual function), more communicationpaths have to be computed by the SM and more Subnet Management Packets(SMPs) have to be sent to the switches in order to update their LFTs.For example, the computation of the communication paths might takeseveral minutes in large networks. Because LID space is limited to 49151unicast LIDs, and as each VM (via a VF), physical node, and switchoccupies one LID each, the number of physical nodes and switches in thenetwork limits the number of active VMs, and vice versa.

InfiniBand SR-IOV Architecture Models—Virtual Port (vPort)

FIG. 6 shows an exemplary vPort concept, in accordance with anembodiment. As depicted in the figure, a host 300 (e.g., a host channeladapter) can interact with a hypervisor 410, which can assign thevarious virtual functions 330, 340, 350, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 310.

In accordance with an embodiment, the vPort concept is loosely definedin order to give freedom of implementation to vendors (e.g. thedefinition does not rule that the implementation has to be SRIOVspecific), and a goal of the vPort is to standardize the way VMs arehandled in subnets. With the vPort concept, both SR-IOV Shared-Port-likeand vSwitch-like architectures or a combination of both, that can bemore scalable in both the space and performance domains, can be defined.A vPort supports optional LIDs, and unlike the Shared-Port, the SM isaware of all the vPorts available in a subnet even if a vPort is notusing a dedicated LID.

InfiniBand SR-IOV Architecture Models—vSwitch with Prepopulated LIDs

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with prepopulatedLIDs.

FIG. 7 shows an exemplary vSwitch architecture with prepopulated LIDs,in accordance with an embodiment. As depicted in the figure, a number ofswitches 501-504 can provide communication within the network switchedenvironment 600 (e.g., an IB subnet) between members of a fabric, suchas an InfiniBand fabric. The fabric can include a number of hardwaredevices, such as host channel adapters 510, 520, 530. Each of the hostchannel adapters 510, 520, 530, can in turn interact with a hypervisor511, 521, and 531, respectively. Each hypervisor can, in turn, inconjunction with the host channel adapter it interacts with, setup andassign a number of virtual functions 514, 515, 516, 524, 525, 526, 534,535, 536, to a number of virtual machines. For example, virtual machine1 550 can be assigned by the hypervisor 511 to virtual function 1 514.Hypervisor 511 can additionally assign virtual machine 2 551 to virtualfunction 2 515, and virtual machine 3 552 to virtual function 3 516.Hypervisor 531 can, in turn, assign virtual machine 4 553 to virtualfunction 1 534. The hypervisors can access the host channel adaptersthrough a fully featured physical function 513, 523, 533, on each of thehost channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 600.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with prepopulatedLIDs. Referring to FIG. 7, the LIDs are prepopulated to the variousphysical functions 513, 523, 533, as well as the virtual functions514-516, 524-526, 534-536 (even those virtual functions not currentlyassociated with an active virtual machine). For example, physicalfunction 513 is prepopulated with LID 1, while virtual function 1 534 isprepopulated with LID 10. The LIDs are prepopulated in an SR-IOVvSwitch-enabled subnet when the network is booted. Even when not all ofthe VFs are occupied by VMs in the network, the populated VFs areassigned with a LID as shown in FIG. 7.

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

In accordance with an embodiment, in a vSwitch architecture withprepopulated LIDs, each hypervisor can consume one LID for itselfthrough the PF and one more LID for each additional VF. The sum of allthe VFs available in all hypervisors in an IB subnet, gives the maximumamount of VMs that are allowed to run in the subnet. For example, in anIB subnet with 16 virtual functions per hypervisor in the subnet, theneach hypervisor consumes 17 LIDs (one LID for each of the 16 virtualfunctions plus one LID for the physical function) in the subnet. In suchan IB subnet, the theoretical hypervisor limit for a single subnet isruled by the number of available unicast LIDs and is: 2891 (49151available LIDs divided by 17 LIDs per hypervisor), and the total numberof VMs (i.e., the limit) is 46256 (2891 hypervisors times 16 VFs perhypervisor). (In actuality, these numbers are actually smaller sinceeach switch, router, or dedicated SM node in the IB subnet consumes aLID as well). Note that the vSwitch does not need to occupy anadditional LID as it can share the LID with the PF

In accordance with an embodiment, in a vSwitch architecture withprepopulated LIDs, communication paths are computed for all the LIDs thefirst time the network is booted. When a new VM needs to be started thesystem does not have to add a new LID in the subnet, an action thatwould otherwise cause a complete reconfiguration of the network,including path recalculation, which is the most time consuming part.Instead, an available port for a VM is located (i.e., an availablevirtual function) in one of the hypervisors and the virtual machine isattached to the available virtual function.

In accordance with an embodiment, a vSwitch architecture withprepopulated LIDs also allows for the ability to calculate and usedifferent paths to reach different VMs hosted by the same hypervisor.Essentially, this allows for such subnets and networks to use a LID MaskControl (LMC) like feature to provide alternative paths towards onephysical machine, without being bound by the limitation of the LMC thatrequires the LIDs to be sequential. The freedom to use non-sequentialLIDs is particularly useful when a VM needs to be migrated and carry itsassociated LID to the destination.

In accordance with an embodiment, along with the benefits shown above ofa vSwitch architecture with prepopulated LIDs, certain considerationscan be taken into account. For example, because the LIDs areprepopulated in an SR-IOV vSwitch-enabled subnet when the network isbooted, the initial path computation (e.g., on boot-up) can take longerthan if the LIDs were not pre-populated.

InfiniBand SR-IOV Architecture Models—vSwitch with Dynamic LIDAssignment

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with dynamic LIDassignment.

FIG. 8 shows an exemplary vSwitch architecture with dynamic LIDassignment, in accordance with an embodiment. As depicted in the figure,a number of switches 501-504 can provide communication within thenetwork switched environment 700 (e.g., an IB subnet) between members ofa fabric, such as an InfiniBand fabric. The fabric can include a numberof hardware devices, such as host channel adapters 510, 520, 530. Eachof the host channel adapters 510, 520, 530, can in turn interact with ahypervisor 511, 521, 531, respectively. Each hypervisor can, in turn, inconjunction with the host channel adapter it interacts with, setup andassign a number of virtual functions 514, 515, 516, 524, 525, 526, 534,535, 536, to a number of virtual machines. For example, virtual machine1 550 can be assigned by the hypervisor 511 to virtual function 1 514.Hypervisor 511 can additionally assign virtual machine 2 551 to virtualfunction 2 515, and virtual machine 3 552 to virtual function 3 516.Hypervisor 531 can, in turn, assign virtual machine 4 553 to virtualfunction 1 534. The hypervisors can access the host channel adaptersthrough a fully featured physical function 513, 523, 533, on each of thehost channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 700.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with dynamic LIDassignment. Referring to FIG. 8, the LIDs are dynamically assigned tothe various physical functions 513, 523, 533, with physical function 513receiving LID 1, physical function 523 receiving LID 2, and physicalfunction 533 receiving LID 3. Those virtual functions that areassociated with an active virtual machine can also receive a dynamicallyassigned LID. For example, because virtual machine 1 550 is active andassociated with virtual function 1 514, virtual function 514 can beassigned LID 5. Likewise, virtual function 2 515, virtual function 3516, and virtual function 1 534 are each associated with an activevirtual function. Because of this, these virtual functions are assignedLIDs, with LID 7 being assigned to virtual function 2 515, LID 11 beingassigned to virtual function 3 516, and LID 9 being assigned to virtualfunction 1 534. Unlike vSwitch with prepopulated LIDs, those virtualfunctions not currently associated with an active virtual machine do notreceive a LID assignment.

In accordance with an embodiment, with the dynamic LID assignment, theinitial path computation can be substantially reduced. When the networkis booting for the first time and no VMs are present then a relativelysmall number of LIDs can be used for the initial path calculation andLFT distribution.

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

In accordance with an embodiment, when a new VM is created in a systemutilizing vSwitch with dynamic LID assignment, a free VM slot is foundin order to decide on which hypervisor to boot the newly added VM, and aunique non-used unicast LID is found as well. However, there are noknown paths in the network and the LFTs of the switches for handling thenewly added LID. Computing a new set of paths in order to handle thenewly added VM is not desirable in a dynamic environment where severalVMs may be booted every minute. In large IB subnets, computing a new setof routes can take several minutes, and this procedure would have torepeat each time a new VM is booted.

Advantageously, in accordance with an embodiment, because all the VFs ina hypervisor share the same uplink with the PF, there is no need tocompute a new set of routes. It is only needed to iterate through theLFTs of all the physical switches in the network, copy the forwardingport from the LID entry that belongs to the PF of the hypervisor—wherethe VM is created—to the newly added LID, and send a single SMP toupdate the corresponding LFT block of the particular switch. Thus thesystem and method avoids the need to compute a new set of routes.

In accordance with an embodiment, the LIDs assigned in the vSwitch withdynamic LID assignment architecture do not have to be sequential. Whencomparing the LIDs assigned on VMs on each hypervisor in vSwitch withprepopulated LIDs versus vSwitch with dynamic LID assignment, it isnotable that the LIDs assigned in the dynamic LID assignmentarchitecture are non-sequential, while those prepopulated in aresequential in nature. In the vSwitch dynamic LID assignmentarchitecture, when a new VM is created, the next available LID is usedthroughout the lifetime of the VM. Conversely, in a vSwitch withprepopulated LIDs, each VM inherits the LID that is already assigned tothe corresponding VF, and in a network without live migrations, VMsconsecutively attached to a given VF get the same LID.

In accordance with an embodiment, the vSwitch with dynamic LIDassignment architecture can resolve the drawbacks of the vSwitch withprepopulated LIDs architecture model at a cost of some additionalnetwork and runtime SM overhead. Each time a VM is created, the LFTs ofthe physical switches in the subnet are updated with the newly added LIDassociated with the created VM. One subnet management packet (SMP) perswitch is needed to be sent for this operation. The LMC-likefunctionality is also not available, because each VM is using the samepath as its host hypervisor. However, there is no limitation on thetotal amount of VFs present in all hypervisors, and the number of VFsmay exceed that of the unicast LID limit. Of course, not all of the VFsare allowed to be attached on active VMs simultaneously if this is thecase, but having more spare hypervisors and VFs adds flexibility fordisaster recovery and optimization of fragmented networks when operatingclose to the unicast LID limit.

InfiniBand SR-IOV Architecture Models—vSwitch with Dynamic LIDAssignment and Prepopulated LIDs

FIG. 9 shows an exemplary vSwitch architecture with vSwitch with dynamicLID assignment and prepopulated LIDs, in accordance with an embodiment.As depicted in the figure, a number of switches 501-504 can providecommunication within the network switched environment 800 (e.g., an IBsubnet) between members of a fabric, such as an InfiniBand fabric. Thefabric can include a number of hardware devices, such as host channeladapters 510, 520, 530. Each of the host channel adapters 510, 520, 530,can in turn interact with a hypervisor 511, 521, and 531, respectively.Each hypervisor can, in turn, in conjunction with the host channeladapter it interacts with, setup and assign a number of virtualfunctions 514, 515, 516, 524, 525, 526, 534, 535, 536, to a number ofvirtual machines. For example, virtual machine 1 550 can be assigned bythe hypervisor 511 to virtual function 1 514. Hypervisor 511 canadditionally assign virtual machine 2 551 to virtual function 2 515.Hypervisor 521 can assign virtual machine 3 552 to virtual function 3526. Hypervisor 531 can, in turn, assign virtual machine 4 553 tovirtual function 2 535. The hypervisors can access the host channeladapters through a fully featured physical function 513, 523, 533, oneach of the host channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 800.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a hybrid vSwitch architecture withdynamic LID assignment and prepopulated LIDs. Referring to FIG. 9,hypervisor 511 can be arranged with vSwitch with prepopulated LIDsarchitecture, while hypervisor 521 can be arranged with vSwitch withprepopulated LIDs and dynamic LID assignment. Hypervisor 531 can bearranged with vSwitch with dynamic LID assignment. Thus, the physicalfunction 513 and virtual functions 514-516 have their LIDs prepopulated(i.e., even those virtual functions not attached to an active virtualmachine are assigned a LID). Physical function 523 and virtual function1 524 can have their LIDs prepopulated, while virtual function 2 and 3,525 and 526, have their LIDs dynamically assigned (i.e., virtualfunction 2 525 is available for dynamic LID assignment, and virtualfunction 3 526 has a LID of 11 dynamically assigned as virtual machine 3552 is attached). Finally, the functions (physical function and virtualfunctions) associated with hypervisor 3 531 can have their LIDsdynamically assigned. This results in virtual functions 1 and 3, 534 and536, are available for dynamic LID assignment, while virtual function 2535 has LID of 9 dynamically assigned as virtual machine 4 553 isattached there.

In accordance with an embodiment, such as that depicted in FIG. 9, whereboth vSwitch with prepopulated LIDs and vSwitch with dynamic LIDassignment are utilized (independently or in combination within anygiven hypervisor), the number of prepopulated LIDs per host channeladapter can be defined by a fabric administrator and can be in the rangeof 0<=prepopulated VFs<=Total VFs (per host channel adapter), and theVFs available for dynamic LID assignment can be found by subtracting thenumber of prepopulated VFs from the total number of VFs (per hostchannel adapter).

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

InfiniBand—Inter Subnet Communication (Fabric Manager)

In accordance with an embodiment, in addition to providing an InfiniBandfabric within a single subnet, embodiments of the current disclosure canalso provide for an InfiniBand fabric that spans two or more subnets.

FIG. 10 shows an exemplary multi-subnet InfiniBand fabric, in accordancewith an embodiment. As depicted in the figure, within subnet A 1000, anumber of switches 1001-1004 can provide communication within subnet A1000 (e.g., an IB subnet) between members of a fabric, such as anInfiniBand fabric. The fabric can include a number of hardware devices,such as, for example, channel adapter 1010. Host channel adapter 1010can in turn interact with a hypervisor 1011. The hypervisor can, inturn, in conjunction with the host channel adapter it interacts with,setup a number of virtual functions 1014. The hypervisor canadditionally assign virtual machines to each of the virtual functions,such as virtual machine 1 1015 being assigned to virtual function 11014. The hypervisor can access their associated host channel adaptersthrough a fully featured physical function, such as physical function1013, on each of the host channel adapters. Within subnet B 1040, anumber of switches 1021-1024 can provide communication within subnet B1040 (e.g., an IB subnet) between members of a fabric, such as anInfiniBand fabric. The fabric can include a number of hardware devices,such as, for example, channel adapter 1030. Host channel adapter 1030can in turn interact with a hypervisor 1031. The hypervisor can, inturn, in conjunction with the host channel adapter it interacts with,setup a number of virtual functions 1034. The hypervisor canadditionally assign virtual machines to each of the virtual functions,such as virtual machine 2 1035 being assigned to virtual function 21034. The hypervisor can access their associated host channel adaptersthrough a fully featured physical function, such as physical function1033, on each of the host channel adapters. It is noted that althoughonly one host channel adapter is shown within each subnet (i.e., subnetA and subnet B), it is to be understood that a plurality of host channeladapters, and their corresponding components, can be included withineach subnet.

In accordance with an embodiment, each of the host channel adapters canadditionally be associated with a virtual switch, such as virtual switch1012 and virtual switch 1032, and each HCA can be set up with adifferent architecture model, as discussed above. Although both subnetswithin FIG. 10 are shown as using a vSwitch with prepopulated LIDarchitecture model, this is not meant to imply that all such subnetconfigurations must follow a similar architecture model.

In accordance with an embodiment, at least one switch within each subnetcan be associated with a router, such as switch 1002 within subnet A1000 being associated with router 1005, and switch 1021 within subnet B1040 being associated with router 1006.

In accordance with an embodiment, at least one device (e.g., a switch, anode . . . etc.) can be associated with a fabric manager (not shown).The fabric manager can be used, for example, to discover inter-subnetfabric topology, create a fabric profile (e.g., a virtual machine fabricprofile), build virtual machine related database objects that forms thebasis for building a virtual machine fabric profile. In addition, thefabric manager can define legal inter-subnet connectivity in terms ofwhich subnets are allowed to communicate via which router ports usingwhich partition numbers.

In accordance with an embodiment, when traffic at an originating source,such as virtual machine 1 within subnet A, is addressed to a destinationin a different subnet, such as virtual machine 2 within subnet B, thetraffic can be addressed to the router within subnet A, i.e., router1005, which can then pass the traffic to subnet B via its link withrouter 1006.

Virtual Dual Port Router

In accordance with an embodiment, a dual port router abstraction canprovide a simple way for enabling subnet-to-subnet router functionalityto be defined based on a switch hardware implementation that has theability to do GRH (global route header) to LRH (local route header)conversion in addition to performing normal LRH based switching.

In accordance with an embodiment, a virtual dual-port router canlogically be connected outside a corresponding switch port. This virtualdual-port router can provide an InfiniBand specification compliant viewto a standard management entity, such as a Subnet Manager.

In accordance with an embodiment, a dual-ported router model impliesthat different subnets can be connected in a way where each subnet fullycontrols the forwarding of packets as well as address mappings in theingress path to the subnet, and without impacting the routing andlogical connectivity within either of the incorrectly connected subnets.

In accordance with an embodiment, in a situation involving anincorrectly connected fabric, the use of a virtual dual-port routerabstraction can also allow a management entity, such as a Subnet Managerand IB diagnostic software, to behave correctly in the presence ofun-intended physical connectivity to a remote subnet.

FIG. 11 shows an interconnection between two subnets in a highperformance computing environment, in accordance with an embodiment.Prior to configuration with a virtual dual port router, a switch 1120 insubnet A 1101 can be connected through a switch port 1121 of switch1120, via a physical connection 1110, to a switch 1130 in subnet B 1102,via a switch port 1131 of switch 1130. In such an embodiment, eachswitch port, 1121 and 1131, can act both as switch ports and routerports.

In accordance with an embodiment, a problem with this configuration isthat a management entity, such as a subnet manager in an InfiniBandsubnet, cannot distinguish between a physical port that is both a switchport and a router port. In such a situation, a SM can treat the switchport as having a router port connected to that switch port. But if theswitch port is connected to another subnet, via, for example, a physicallink, with another subnet manager, then the subnet manager can be ableto send a discovery message out on the physical link. However, such adiscovery message cannot be allowed at the other subnet.

FIG. 12 shows an interconnection between two subnets via a dual-portvirtual router configuration in a high performance computingenvironment, in accordance with an embodiment.

In accordance with an embodiment, after configuration, a dual-portvirtual router configuration can be provided such that a subnet managersees a proper end node, signifying an end of the subnet that the subnetmanager is responsible for.

In accordance with an embodiment, at a switch 1220 in subnet A 1201, aswitch port can be connected (i.e., logically connected) to a routerport 1211 in a virtual router 1210 via a virtual link 1223. The virtualrouter 1210 (e.g., a dual-port virtual router), which while shown asbeing external to the switch 1220 can, in embodiments, be logicallycontained within the switch 1220, can also comprise a second routerport, router port II 1212. In accordance with an embodiment, a physicallink 1203, which can have two ends, can connect the subnet A 1201 viafirst end of the physical link with subnet B 1202 via a second end ofthe physical link, via router port II 1212 and router port II 1232,contained in virtual router 1230 in subnet B 1202. Virtual router 1230can additionally comprise router port 1231, which can be connected(i.e., logically connected) to switch port 1241 on switch 1240 via avirtual link 1233.

In accordance with an embodiment, a subnet manager (not shown) on subnetA can detect router port 1211, on virtual router 1210 as an end point ofthe subnet that the subnet manager controls. The dual-port virtualrouter abstraction can allow the subnet manager on subnet A to deal withsubnet A in a usual manner (e.g., as defined per the InifiniBandspecification). At the subnet management agent level, the dual-portvirtual router abstraction can be provided such that the SM sees thenormal switch port, and then at the SMA level, the abstraction thatthere is another port connected to the switch port, and this port is arouter port on a dual-port virtual router. In the local SM, aconventional fabric topology can continue to be used (the SM sees theport as a standard switch port in the topology), and thus the SM seesthe router port as an end port. Physical connection can be made betweentwo switch ports that are also configured as router ports in twodifferent subnets.

In accordance with an embodiment, the dual-port virtual router can alsoresolve the issue that a physical link could be mistakenly connected tosome other switch port in the same subnet, or to a switch port that wasnot intended to provide a connection to another subnet. Therefore, themethods and systems described herein also provide a representation ofwhat is on the outside of a subnet.

In accordance with an embodiment, within a subnet, such as subnet A, alocal SM determines a switch port, and then determines a router portconnected to that switch port (e.g., router port 1211 connected, via avirtual link 1223, to switch port 1221). Because the SM sees the routerport 1211 as the end of the subnet that the SM manages, the SM cannotsend discovery and/or management messages beyond this point (e.g., torouter port II 1212).

In accordance with an embodiment, the dual-port virtual router describedabove provides a benefit that the dual-port virtual router abstractionis entirely managed by a management entity (e.g., SM or SMA) within thesubnet that the dual-port virtual router belongs to. By allowingmanagement solely on the local side, a system does not have to providean external, independent management entity. That is, each side of asubnet to subnet connection can be responsible for configuring its owndual-port virtual router.

In accordance with an embodiment, in a situation where a packet, such asan SMP, is addressed to a remote destination (i.e., outside of the localsubnet) arrives at a local target port that is not configured as a thedual-port virtual router described above, then the local port can returna message specifying that it is not a router port.

Many features of the present invention can be performed in, using, orwith the assistance of hardware, software, firmware, or combinationsthereof. Consequently, features of the present invention may beimplemented using a processing system (e.g., including one or moreprocessors).

FIG. 13 shows a method for supporting dual-port virtual router in a highperformance computing environment, in accordance with an embodiment. Atstep 1310, the method can provide at one or more computers, includingone or more microprocessors, a first subnet, the first subnet comprisinga plurality of switches, the plurality of switches comprising at least aleaf switch, wherein each of the plurality of switches comprise aplurality of switch ports, a plurality of host channel adapters, eachhost channel adapters comprising at least one host channel adapter port,a plurality of end nodes, wherein each of the end nodes are associatedwith at least one host channel adapter of the plurality of host channeladapters, and a subnet manager, the subnet manager running on one of theplurality of switches and the plurality of host channel adapters.

At step 1320, the method can configure a switch port of the plurality ofswitch ports on a switch of the plurality of switches as a router port.

At step 1330, the method can logically connect the switch portconfigured as the router port to a virtual router, the virtual routercomprising at least two virtual router ports.

Router SMA Abstraction in Order to Allow SMP-Based Connectivity Checks

In accordance with an embodiment, a Subnet Management Packet (SMP) isnot allowed to have addressing information that implies that the packetwill be sent beyond router ports. However, in order to allow discoveryof physical connectivity on the remote side of a (virtual) router port(that is, local discovery of remote connectivity), a new set of SMAattributes can be defined, where each such new attribute represents anindication of “remote information” along with either a standard orvendor specific SMA attribute.

In accordance with an embodiment, when a router SMA processes attributesthat represent “remote” information/attributes, then a corresponding SMPrequest can be sent on the external physical link in a way that is fullytransparent to the sender of the original request.

In accordance with an embodiment, a local SMA can chose to performremote discovery independently of incoming requests and then cacherelevant information locally, or it can act like a simple proxy andgenerate a corresponding request to the external link each time itreceives a request specifying “remote” information/attributes.

In accordance with an embodiment, by tracking whether an SMP requestinga “remote” attribute is received from the local subnet side (i.e., thevirtual router port that is logically connected to the local switchport) or from the external link (i.e., the remote side of the virtualrouter), the SMA implementation can track to what extent the remoterequest is valid in terms of either representing the original request inthe local subnet or representing a proxy request from a peer routerport.

In accordance with an embodiment, for an IB specification compliant SM,a router port is an end port in a subnet. Because of this, low-levelSMPs (used to discovery and configure the subnet) cannot be sent acrossa router port. However, in order to maintain routes for inter-subnettraffic, a local SM or fabric manager needs to be able to observe thephysical connectivity on a remote side of a physical link before itmakes any configuration of the local resources. However, in connectionwith this desire to see the remote connectivity, a SM cannot be allowedto configure the remote side of a physical link (that is, a SM'sconfiguration must be contained within its own subnet).

In accordance with an embodiment, SMA model enhancements allow for thepossibility to send a packet (i.e., SMP) that is addressed to a localrouter port. The SMA where the packet is addressed can receive thepacket, and then apply a new attribute that defines that the requestedinformation is on a remote node (e.g., connected by a physical linkacross subnets).

In accordance with an embodiment, the SMA can operate as a proxy(receives an SMP and sends another request), or the SMA can modify theoriginal packet and sent it on as an inter-subnet packet. The SMA canupdate the address information in the packet. This update the additionof a 1-hop direct route path to the SMP. The SMP can then be received bythe remote node (router port). The SMP can work independently of whetheror not the node on the remote end is configured in the same manner(e.g., as a virtual router), or configured as a basic switch port (e.g.,physical connectivity to a legacy switch implementation). Then therequest packet that the receiving node will see is a basic request, andit will respond in the normal way. The fact that the request originatedbeyond the subnet is transparent (invisible) to the receiving node.

In accordance with an embodiment, this allows for remote subnetdiscovery, by a local subnet, by utilizing the abstraction. The providedSMA abstraction allows for the retrieval of information from a remotesubnet (e.g., across a physical link) without the remote side realizingthat it has been queried from the local (i.e., remote to the subnetdiscovery being performed on) subnet.

Addressing Scheme

In accordance with an embodiment, in order to stay compliant with the IBspecification, SMP packets are bound by the boundaries of the subnet(i.e., the SM is not allowed to “see,” or discover information, outsideof the subnet it is associated with). However, there still exists a needto retrieve information, such as connectivity information, from a remoteend of a virtual router port (i.e., one “hop” beyond the subnetboundary). This information can be encoded into a special type of SMP,which can be referred to as a vendor specific SMP (VSMP).

In accordance with an embodiment, a VSMP can generally utilize anaddressing scheme that is similar to a general SMP (subnet bound SMP),both DR (Directed Routing—where an SMP can explicitly indicate whichport it exists from when going from switch to switch) and LID routingcan be used. However, for those attributes that can apply to a remoteend of a router port, a single bit in an attribute modifier can be usedto indicate local port versus remote port. If a remote bit of anattribute is set, then additional handling can occur at the SMArepresenting the router port.

In accordance with an embodiment, an important aspect of the addressingscheme is that the remote peer port of the router port be able torespond to the request, even in case of erroneous configuration orwiring of the system. For instance if the virtual router is connected,via a physical link for example, to a remote subnet at a general switchport of the remote subnet, the SMA handing the general switch port ofthe remote subnet can respond to the request with status valueindicating that the remote attribute is not supported, and the responsecan reach the requesting SM.

In accordance with an embodiment, an SMP (i.e., VSMP) can be sent to alocal router port, either through the use of a DR path or via the LID ofthe router port. If the information requested is for the remote peerport of the router port, then the remote flag/bit of the attributemodifier can be set. When the SMA receives such a VSMP, it can alter thepacket and add an additional DR step addressing the remote end.

In accordance with an embodiment, a portion (e.g., a bit of a 16 bitattribute modifier) of the packet attribute can be used to signalwhether the VSMP is local or remote. For example, by setting thisportion to a value of 1 can imply that the remote peer port is the finaldestination for the VSMP. This portion of the attribute can be referredto as the remote flag.

In accordance with an embodiment, in addition to the remote flag, therecan be additional flags that can indicate which destination instancesthat should process the VSMP along the way to the final destination. Twoadditional portions (e.g., two bits of the attribute modifier) of thepacket attribute can be used for this purpose. A first portion (e.g.,bit 20), referred to as first receiver flag, can indicate that thepacket is expected to be processed when received by the local routerport (which should match the destination address of the originalrequest). When all the expected processing at the first receiver isdone, a second portion (e.g., bit 21 of the attribute modifier) of thepacket attribute can be set and the packet forwarded on to the remoteend. This second portion can be referred to as the second receiver flag.

DR Routed Packet

In accordance with an embodiment, by way of example, a DR routed packetcan follow an exemplary flow. A source node, at LID A, can initiate therequest packet specifying router 1 as the destination node. An exemplaryDR routed packet configuration is here:

-   -   MADHdr.Class=0x81 (DR routed SMP)    -   MADHdr.Method=0x1 (Get)    -   LRH.SLID=LRH.DLID=0xffff (the permissive LID)    -   MADHdr.DrSLID=MADHdr.DrDLID=0xffff    -   MADHdr.AttrID=<VSMP attrID>    -   MADHdr.AttrMod.remote=1    -   MADHdr.AttrMod.first_receiver=1    -   MADHdr.InitPath=DR path to Rtr1 (LID B)    -   MADHdr.HopCnt=N    -   MADHdr.HopPtr=0

When the request packet arrives at router 1, it can be passed on to acorresponding SMA, which can then verify that the request is valid.After verifying the validity of the request, the SMA can then modify thepacket. This modification can include extending the DR path with oneextra hop, and setting the second receiver flag. Such exemplaryconfiguration modification is shown here:

-   -   MADHdr.HopCnt=N+1 (extend the DR path with one extra hop)    -   MADHdr.InitPath[N+1]=(virtual Router external port number (i.e.        2))    -   MADHdr.AttrMod.second_receiver=1

In accordance with an embodiment, the SMI (subnet management interface)layer of the SMA can update the DR with the extra hop before the SMAforwards the VSMP out on the physical link.

In accordance with an embodiment, for the SMA that receives the VSMP onthe remote side of the physical link, the addressing scheme used by theVSMP can appear to be that of a normally IB defined packet.

In accordance with an embodiment, when the SMA receiving the VSMP on theremote side of the physical link is the VSMP's final destination, theVSMP can be validated by the received SMA. The validation can includechecking input port relative to flag settings. If remote flag and bothfirst and second receive flags are set, then the packet can be receivedon the physical port (i.e., from the external link side of the portconfigured with the virtual router). If remote and only the firstreceiver flag are set, then the packet can arrive on the virtual ink(i.e., from the internal switch side of the virtual router port). If thevalidation fails, then the status can be set to an appropriate errormessage.

FIG. 14 is a flow chart illustrating a DR routed VSMP packet, inaccordance with an embodiment.

At step 1401, in accordance with an embodiment, within subnet A, anentity, such as a subnet manager of subnet A can request, via a DRrouted VSMP, connectivity information. The destination of the DR routedVSMP can be a router within subnet A, such as router 1.

At step 1402, the DR routed VSMP can arrive at router 1. Router 1, in anembodiment and as described above, can be contained in a switch, such asswitch 1. The DR routed VSMP can be passed to the SMA of switch 1 forverification.

At step 1403, in accordance with an embodiment, the SMA can modify theDR routed VSMP. The modification can include extending the hop counter(for the hop across the physical link to the second subnet), and settingthe second receiver flag.

At step 1404, in accordance with an embodiment, the SMI (the SMI beingassociated with the SMA of the switch/router) can update the hop pointerof the VSMP.

At step 1405, in accordance with an embodiment, the SMI can forward theDR VSMP across the subnet boundary between subnet A 1420 and subnet B1430, on a physical link, where a first end of the physical link can beconnected to the router within subnet A, and the second end of thephysical link can be connected to a router within subnet B.

At step 1406, in accordance with an embodiment, SMA′ of the router 2within subnet B 1430 can receive the VSMP from the physical link.

At step 1407, in accordance with an embodiment, SMI′ (associated withSMA′) can validate the VSMP request.

In accordance with an embodiment, the responding entity (e.g., therouter on the remote side of the physical link) can complete the SMPresponse and set a direction attribute indicating a response. Such anexemplary configuration is shown here:

-   -   MADHdr.Method=0x81 (GetResp)    -   MADHdr.Direction=1 (indicating response)

In accordance with an embodiment, the SMI layer can then decrement thehop pointer and forward the response out on the physical link, back tothe local side. The SMA at the local router can revert the modificationsmade on the request. The SMI at the local side router can perform thenormal processing, including decrementing the hop and sending theresponse out on the virtual link to the switch (i.e., on the internalvirtual link between the switch port and the virtual router port). Forthe next hop, the SMI can again decrement the hop and send the packetout on the physical switch port where the request originally arrived.

FIG. 15 is a flow chart illustrating a response to a DR routed VSMPpacket, in accordance with an embodiment.

At step 1501, in accordance with an embodiment, SMA′ of router 2 canfill in the responsive information to the VSMP (e.g., connectivityinformation), and set a directional flag in to indicate a response.

At step 1502, in accordance with an embodiment, SMI′ can decrement thehop pointer of the response and forward the response back from subnet B1530 to subnet A 1520 on, for example, a physical link having two ends.A first end of the physical link can be connected to the router withinsubnet A, and the second end of the physical link can be connected to arouter within subnet B.

At step 1503, in accordance with an embodiment, the SMA at router 1 canreceive the response and revert the modifications done on the VSMP.

At step 1504, in accordance with an embodiment, the SMI at router 1 canprocess the response to the VSMP and send the response on a link (e.g.,virtual link between the virtual router 1 and the physical switch) tothe physical switch.

At step 1505, in accordance with an embodiment, the SMI can decrementthe hop point counter and send the packet out on the physical switchport where the VSMP was originally received.

LID Routed Packet

In accordance with an embodiment, by way of example, a LID routed packetcan follow an exemplary flow. A source node, at LID A, can initiate therequest packet specifying router 1 as the destination node. Such anexemplary packet could have the following configuration:

-   -   MADHdr.Class=0x01 (LID routed SMP)    -   MADHdr.Method=0x1 (Get)    -   LRH.SLID=LID A    -   LRH.DLID=LID B    -   MADHdr.AttrID=<VSMP attrID>    -   MADHdr.AttrMod.remote=1    -   MADHdr.AttrMod.first_receiver=1

In accordance with an embodiment, when the request packet arrives atrouter 1, it can be passed on to a corresponding SMA, which can thenverify that the request is valid. After verifying the validity of therequest, the SMA can then modify the packet. This modification caninclude adding a single DR path at the end. Consequently, this meansthat the total address can be a combination of both a LID routed packetand a DR routed hop. An exemplary configuration is here:

-   -   MADHdr.Class=0x81 (DR routed SMP)    -   MADHdr.HopCnt=1    -   MADHdr.HopPtr=0    -   MADHdr.Direction=0 (outbound)    -   MADHdr.InitPath[1]=(virtual Router external port number (i.e.        2))    -   MADHdr.DrSLID=LRH.SLID (I.e. LRH.SLID contains LID A from the        original requester)    -   MADHdr.DrDLID=0xffff    -   MADHdr.AttrMod.second_receiver=1

In accordance with an embodiment, an SMI layer at the router can processthe outbound packet normally, and send it out on the physical link. Anexemplary configuration is here:

-   -   LRH.SLID=LRH.DLID=0xffff    -   MADHdr.HopPtr=1 (increment by 1)

In accordance with an embodiment, the SMI at the destination router (atthe other end of the physical link) can determine that it is thedestination for the request and pass the VSMP onto the associated SMA.

FIG. 16 is a flow chart illustrating a LID routed VSMP packet, inaccordance with an embodiment.

At step 1601, in accordance with an embodiment, within subnet A, anentity, such as a subnet manager of subnet A can request, via a LIDrouted VSMP, connectivity information. The destination of the LID routedVSMP can be a router within subnet A, such as router 1.

At step 1602, the LID routed VSMP can arrive at router 1. Router 1, inan embodiment and as described above, can be contained in a switch, suchas switch 1. The LID routed VSMP can be passed to the SMA of switch 1for verification.

At step 1603, in accordance with an embodiment, the SMA can modify theDR routed VSMP. The modification can include adding a single hop DRrouted path to the end of the address, extending the hop counter (forthe hop across the physical link to the second subnet), and setting thesecond receiver flag.

At step 1604, in accordance with an embodiment, the SMI (the SMI beingassociated with the SMA of the switch/router) can update the hop pointerof the VSMP.

At step 1605, in accordance with an embodiment, the SMI can forward theoriginally LID routed VSMP across the subnet boundary between subnet A1620 and subnet B 1630, on a physical link, where a first end of thephysical link can be connected to the router within subnet A, and thesecond end of the physical link can be connected to a router withinsubnet B.

At step 1606, in accordance with an embodiment, SMA′ of the router 2within subnet B 1630 can receive the now DR routed VSMP from thephysical link.

At step 1607, in accordance with an embodiment, SMI′ (associated withSMA′) can validate the VSMP request.

In accordance with an embodiment, for a response flow, the SMA at router2 can validate the VSMP. The validation can include checking input portrelative to flag settings. If remote flag and both first and secondreceive flags are set, then the packet can be received on the physicalport (i.e., from the external link side of the port configured with thevirtual router). If remote and only the first receiver flag are set,then the packet can arrive on the virtual ink (i.e., from the internalswitch side of the virtual router port). If the validation fails, thenthe status can be set to an appropriate error message.

In accordance with an embodiment, the SMA′ at router 2 can complete theSMP response and set a direction attribute indicating a response. Suchan exemplary configuration is shown here:

-   -   MADHdr.Method=0x81 (GetResp)    -   MADHdr.Direction=1 (indicating response)    -   LRH.SLID=0xffff    -   LRH.DLID=ReqMAD.MADHdr.SLID=0xffff

The SMI′ at router 2 can then decrement the hop pointer and forward theresponse out on the physical link, back to router 1. The SMA at router 1can then revert the modifications performed on the original request,before forwarding the response out of the physical switch port back tothe source. An exemplary configuration after such reversal is here:

-   -   MADHdr.Class=0x01    -   LRH.DLID=MADHdr.DrSLID (i.e. contains LID A from the original        requester)    -   LRH.SLID=local LID=B

In accordance with an embodiment, the SMA can additionally clear the DRspecific fields of the VSMP so that the response appears to becompletely consistent with the original VSMP when the response arrivesat the original requestor.

In accordance with an embodiment, once the response arrives back at thesource, the source will see a normally router LID response, just as ifit had been processed entirely at router 1.

FIG. 16 is a flow chart illustrating a response to a LID routed VSMPpacket, in accordance with an embodiment.

At step 1701, in accordance with an embodiment, SMA′ of router 2 canfill in the responsive information to the VSMP (e.g., connectivityinformation), and set a directional flag in to indicate a response.

At step 1702, in accordance with an embodiment, SMI′ can decrement thehop pointer of the response and forward the response back from subnet B1730 to subnet A 1720 on, for example, a physical link having two ends.A first end of the physical link can be connected to the router withinsubnet A, and the second end of the physical link can be connected to arouter within subnet B.

At step 1703, in accordance with an embodiment, the SMA at router 1 canreceive the response and revert the modifications done on the VSMP,including taking off the DR routed hop.

At step 1704, in accordance with an embodiment, the SMI at router 1 canprocess the response to the VSMP and send the LID routed response out onthe physical switch port where the VSMP was originally received.

SMA Abstraction for Router Ports for Control-Plane Address Discovery

In accordance with an embodiment, in order for management entities inconnected IB subnets to be able to communicate, an SMA abstraction canbe utilized to establish relevant IB address information withoutdependency on out-of-band communication or explicit configuration inputto each subnet.

In accordance with an embodiment, by utilizing SMA attributes at therelevant router ports that identify the GID/GUID of the managemententity as well as any additional address information (e.g., in terms ofQP numbers, Q_Keys . . . etc.) it is possible for management entities(i.e., subnet managers) in each local subnet to keep track of theidentity of the remote peers using SMP based probing of the relevantremote router port information.

In accordance with an embodiment, every local subnet can update theinformation in the router port SMAs, as well as updating forwarding ofrelevant DGIDs in the local subnet to ensure correct forwarding.

In accordance with an embodiment, such update operations can take placeas part of initial subnet configuration, following any change in(virtual) router connectivity or configuration, as well as following anychange of management mastership or other fail-over actions.

In accordance with an embodiment, such methods and systems can allow forboth the use of fixed GIDs that are used independently of localdestination nodes as well as updates of GID information as part offail-over handling. As well, such methods and systems also provide formulticast addressing, and having requests be forwarded to both masterentities and standby entities at the same time.

In accordance with an embodiment, by having the SMA attributes at routerports confined to each subnet, independently, each subnet retainscontrol over the configuration of such SMA attributes without dependingon any unicast or multicast GID values being well known across subnetboundaries.

In accordance with an embodiment, and as mentioned above, a subnet hasat least one subnet manager. Each SM resides on a port of a CA (channeladapter), router, or switch and can be implemented either in hardware orsoftware. When there are multiple SMs on a subnet, one SM can be themaster SM. The remaining SMs must be standby SMs. There is only one SMper port.

In accordance with an embodiment, the master SM is a key element ininitializing and configuring an IB subnet. The master SM is elected aspart of the initialization process for the subnet and is responsiblefor, at least: discovering the physical topology of the subnet,assigning Local Identifiers (LIDs) to the endnodes, switches, androuters, establishing possible paths among the endnodes, sweeping thesubnet, discovering topology changes and managing changes as nodes areadded and deleted.

In accordance with an embodiment, the communication between the masterSM and the SMAs (each switch, CA, and router can comprise a SMA managedby the master SM), and among the SMs, is performed with subnetmanagement packets (SMPs). There are generally two types of SMPs: LIDrouted and directed route (DR). LID routed SMPs are forwarded throughthe subnet (by the switches) based on the LID of the destination.Directed route SMPs are forwarded based on a vector of port numbers thatdefine a path through the subnet. Directed route SMPs are used toimplement several management functions, in particular, before the LIDsare assigned to the nodes.

FIG. 18 illustrates a format for a Subnet Management Packet (SMP), inaccordance with an embodiment. More specifically, FIG. 18 shows an LIDrouted SMP packet.

In accordance with an embodiment, an SMP, such as the one depicted inFIG. 18, can comprise a fixed length 256-byte packet, comprising aplurality of fields. The fields can include a common MAD header 1800, anM_Key (management key) 1810, a reserved field of 32 bytes 1820, a SMPdata field of 64 bytes 1830, and a reserved filed of 128 bytes 1840.

In accordance with an embodiment, the common MAD header field can be 24bytes long. The common MAD header field is described in more detail inthe description of FIG. 19.

In accordance with an embodiment, the M_Key 1810 can comprise a 64 bitkey, which is employed for Subnet Manager authentication.

In accordance with an embodiment, the reserved field of 32 bytes 1820can be used for aligning the SMP data field with the directed routed SMPdata field.

In accordance with an embodiment, the SMP data field of 64 bytes 1830can contain the method's attribute. Finally, the reserved field of 128bytes 1140 can be reserved.

FIG. 19 illustrates a common MAD header field, in accordance with anembodiment. The header field can be 24 bytes long and can comprisefields for: BaseVersion, MgmntClass 1900, Class Version, R, Method 1910,Transaction ID, AttributeID 1920, Reserved, and Attribute Modifier 1930.

In accordance with an embodiment, the MgmtClass 1900 field can define amanagement class of the subnet management packet. For example, theMgmtClass value is set to 0x01 for a LID routed class, and to 0x81 for adirected route class. As another example, the value of the MgmtClassfield can be set to a value representing the subnet management classdefining methods and attributes associated with discovering,initializing, and maintaining a given subnet.

In accordance with an embodiment, the method 1910 field defines a methodto perform (as based on the management class defined in the MgmtClassfield). Methods define the operations that a management class supports.Some common management methods include Get( ), which is a request havinga value of 0x01 and allows for a request for an attribute from a node(e.g., channel adapter, switch, or router) in a system; Set( ), which isa request having a value of 0x02 and allows to set an attribute at anode in the system; and GetResp( ) which is a response having a value of0x81, and is a response from an attribute Get( ) or Set( ) request.

In accordance with an embodiment, the AttributeID 1920 can defineobjects that are being operated on, while the management classattributes define the data which a management class works on.Attributes, such as subnet management attributes, are compositestructures made up from components that can represent different piecesof hardware, such as registers in channel adapters, switches, androuters. Each management class defines a set of attributes, and eachattribute within a particular management class can be assigned anAttributeID. The AttributeModifier field 1930 can further modify anapplication of an attribute.

As mentioned above, in accordance with an embodiment, SMPs can be sentby a SM to the various SMAs within the subnet. In some embodiments, SMPsare exclusively addressed to management queue pairs, such as QP0.

FIG. 20 shows a table of the subnet management attributes, and whichmethods can apply to each attribute, in accordance with an embodiment.

In accordance with an embodiment, the IB specification provides for arange of vendor-specified subnet management attributes. These vendorspecified subnet management attributes can be used by vendors forspecific needs. This is shown in FIG. 20 as the RESERVED attribute 2010,having a range from 0xFF00-0xFFFF.

In accordance with an embodiment, a vendor specified subnet managementattribute can comprise an attribute that allows for remote discovery oflocal subnet information. This can facilitate data traffic betweenconnected subnets, each subnet having an independent subnet managerresponsible for the discovery, setup, and management of its own subnet.The different SMs operate without knowing another SM is in anothersubnet. In order to be able to keep track of which connectivity (e.g.,inter-subnet connectivity) to use for different nodes, the managemententities can utilize the vendor specified management attribute in orderto exchange information about connectivity in order to provide optimizeddata traffic between the subnets.

In accordance with an embodiment, when a SM in a local subnet discoversa connected subnet B, it can query node/switch/connectivity informationabout subnet B via the vendor specified subnet management attribute. Byusing the discovered node/switch/connectivity information, the SM insubnet A can set up a mapping such that data traffic is enabled betweenthe subnets. Subnet manager in subnet B can perform similar options withrespect to subnet A.

FIG. 21 illustrates a system for supporting SMA level abstractions atrouter ports for inter-subnet exchange of management information in ahigh performance computing environment, in accordance with anembodiment.

In accordance with an embodiment, within a subnet 2100, a number of hostchannel adapters 2101 and 2102, which one or more of the host channeladapters can support a virtual switch, such as virtual switch 2130 inhost channel adapter 2101 (HCA 2102 can, for example, support one ormore physical hosts (not shown)), respectively, can be interconnectedvia a number of switches, such as switches 2120-2125. As well, thesubnet can host one or more routers, such as router 2126. The SMA (notshown) at the router (e.g., at the switch port configured as a routerport), can be associated with a remote attribute 2110. Additionally, asubnet manager 2150, as described above, can be hosted at a node withinthe subnet 2100. For the sake of convenience, the subnet manager 2150 isnot shown as being hosted by any of the displayed nodes in the subnet.However, one of skill in the art should understand that the subnetmanager 2150 is hosted on a node of the subnet, as described above.

In addition, although not shown, the subnet 2100 can be interconnectedwith additional other subnets, each of which can also support a SMAattribute/abstraction at router ports for inter-subnet exchange ofmanagement information.

In accordance with an embodiment, the remote attribute 2110 can comprisea number of different attributes. For the sake of convenience, only oneblock for the attribute is shown in the figure, but it is to beunderstood that the remote attribute block 2110 can comprise one or manyattributes, which are further described below.

In accordance with an embodiment, the remote attribute 2110 can comprisea remote physical node information attribute (also referred to herein as“RemPhysicalNodeInfo”), which can allow a subnet manager from adifferent subnet (not shown) to observe the physical connectivity of thesubnet 2100.

In accordance with an embodiment, the remote attribute 2110 can comprisea remote switch configuration information attribute (also referred toherein as “RemSwitchConfigInfo”), which can comprise information aboutport configuration within subnet 2100 (i.e., the subnet that theattribute is contained in). In accordance with an embodiment, when anSMP is received from a connected subnet, the RemSwitchConfigInfoattribute can provide, via the SMP from the remote subnet, portconfiguration information to a subnet manager in the connected subnet.

In accordance with an embodiment, these two attributes,RemPhysicalNodeInfo and RemSwitchConfigInfo, can be allowed to berequested via SMP access across a virtual router to retrieve theconfiguration of the remote end too.

In accordance with an embodiment, a subnet manager, such as subnetmanager 2150, can access and configure the remote attribute 2110(whether it is the RemPhysicalNodeInfo attribute, or theRemSwitchConfigInfo attribute, or both) via a SMP packet directed to therouter/switch port configured as a router (e.g., the dual-port virtualrouter embodiment described above). By disallowing configuration accessfrom other management entities, such as a subnet manager in aneighboring/connected subnet, the subnet manager 2150 retains controlover the configuration of the remote attribute 2110.

In accordance with an embodiment, a subnet manager in aneighboring/connected subnet can access the information contained in theremote attribute 2110 via a DR or LID routed vendor specific SMP (VSMP),as described above.

In accordance with an embodiment, information about the remote end canbe retrieved from the local router port itself or alternatively byexplicitly addressing the port that is a single hop (DR path) beyond thelocal router port.

In accordance with an embodiment, a subnet manager that is responsiblefor establishing or configuring the remote attribute can additionally beresponsible for reconfiguring the remote attribute to correspond to anychange of the subnet associated with the subnet manager. For example, ifa switch in the subnet goes offline, the subnet manager, in addition tobeing responsible for reconfiguring the actual subnet, wouldadditionally be responsible for reconfiguring the remote attribute tocorrespond to the reconfigured subnet (i.e., updating connectivityinformation and port status information at the remote attribute).

FIG. 22 is a flow chart of a method for supporting SMA levelabstractions at router ports for inter-subnet exchange of managementinformation in a high performance computing environment, in accordancewith an embodiment.

At step 2210, the method can provide, at one or more computers,including one or more microprocessors, a first subnet, the first subnetcomprising one or more switches, the one or more switches comprising atleast a leaf switch, wherein each of the one or more switches comprise aplurality of switch ports, a plurality of host channel adapters, eachhost channel adapter comprising at least one host channel adapter port,a plurality of end nodes, wherein each of the end nodes are associatedwith at least one host channel adapter of the plurality of host channeladapters, and a subnet manager, the subnet manager running on one of theplurality of switches and the plurality of host channel adapters.

At step 2220, the method can configure a switch port of the plurality ofswitch ports on a switch of the one or more switches as a router port.

At step 2230, the method can logically connect the switch portconfigured as the router port to a virtual router.

At step 2240, the method can provide at the switch of the one or moreswitches that comprises the switch port of the plurality of switch portsconfigured as a router port a remote attribute subnet manager attribute(RASMA), wherein the RASMA comprises information about the first subnet,the information about the first subnet comprising at least one ofconnectivity information and port configuration information.

SMA Abstraction for Router Ports for Enablement of Data Traffic

In accordance with an embodiment, the dual-port virtual router modelthat described above can be used for an abstraction for such twoneighboring subnets are connected via an intermediate “trivial” subnetthat logically just includes the two “external” virtual router portsfrom each of the dual-port virtual routers that have been associatedwith the relevant switch ports. This is shown in FIG. 23, which depictsa trivial intermediate subnet, in accordance with an embodiment. FIG. 23shows an interconnection between two subnets via a dual-port virtualrouter configuration in a high performance computing environment.

In accordance with an embodiment, after configuration, a dual-portvirtual router configuration can be provided such that a subnet managersees a proper end node, signifying an end of the subnet that the subnetmanager is responsible for. As well, a subnet manager can, based uponthe dual-port virtual router configuration at both subnet A and subnetB, detect a trivial intermediate subnet 2305.

In accordance with an embodiment, at a switch 1220 in subnet A 1201, aswitch port can be connected (i.e., logically connected) to a routerport 1211 in a virtual router 1210 via a virtual link 1223. The virtualrouter 1210 (e.g., a dual-port virtual router), which while shown asbeing external to the switch 1220 can, in embodiments, be logicallycontained within the switch 1220, can also comprise a second routerport, router port II 1212. In accordance with an embodiment, a physicallink 1203, which can have two ends, can connect the subnet A 1201 viafirst end of the physical link with subnet B 1202 via a second end ofthe physical link, via router port II 1212 and router port II 1232,contained in virtual router 1230 in subnet B 1202. Virtual router 1230can additionally comprise router port 1231, which can be connected(i.e., logically connected) to switch port 1241 on switch 1240 via avirtual ink 1233.

In accordance with an embodiment, because a subnet manager in a localsubnet, for example subnet A, detects a switch port 1221 logicallyconnected to a router port 1211. The subnet manager, per the IBspecification, determines that router port 1211 is a logical end to thesubnet manager's local subnet. The trivial intermediate subnet 2305 thencomprises two router ports, namely router port II 1212 and router portII 1232, which are logically connected (e.g., via a physical link).

This dual-port virtual router provides several advantages, in accordancewith an embodiment. For example, the dual-port virtual router canmaintain subnet independence when two neighboring subnets are connectedincorrectly. For example, if a local subnet is connected, via adual-port virtual router configuration, to a remote subnet in such a waythat the connection to the remote subnet is at an ordinary switch port(i.e., an error in cabling), then the subnet manager in the remotesubnet would still detect a switch port connected to a router port, andwould not be able to perform operations within the local subnet. Thedual-port virtual router provides an assurance that there is noconfusion among subnet managers in connected subnets.

FIG. 24 is an illustration of a system for SMA abstraction for routerports for enablement of data traffic in a high performance computingenvironment, in accordance with an embodiment.

In accordance with an embodiment, within a subnet 2400, a number of hostchannel adapters 2401 and 2402, which can at least one host channeladapter can support a virtual switch 2403 and 2404 (although not shown,other host channel adapters can support physical hosts without a virtualswitch), respectively, can be interconnected via a number of switches,such as switches 2420-2425. As well, the subnet can host one or morerouters, such as router 2426. The SMA (not shown) at the router (e.g.,at the switch port configured as a router port), can be associated witha data attribute 2410. Additionally, a subnet manager 2450, as describedabove, can be hosted at a node within the subnet 2400. For the sake ofconvenience, the subnet manager 2450 is not shown as being hosted by anyof the displayed nodes in the subnet. However, one of skill in the artshould understand that the subnet manager 2450 is hosted on a node ofthe subnet, as described above.

In accordance with an embodiment, the subnet 2400 can additionallycomprise a number of end nodes, such as end nodes 2430-2435. Note thatwhile the end nodes are shown in the figure as being separate from theHCAs, one of ordinary skill in the art, and by reference to the abovedisclosure, would know that the end nodes can be virtual machinesrunning hosted at the HCA, running on a hypervisor, via one or morevirtual functions. As well, one of ordinary skill in the art would knowthat while only six end nodes are depicted in the figure, a subnet, suchas subnet 2400, can support a greater or fewer number of end nodes.

In accordance with an embodiment, the router 2426 can comprise, asdescribed above, a switch port of a switch, such as switch 2423, whichis configured as a virtual router, such as a dual-port virtual router.

In addition, although not shown, the subnet 2400 can be interconnectedwith additional other subnets, each of which can also support a SMAattribute/abstraction at router ports for inter-subnet exchange ofmanagement information.

In accordance with an embodiment, and as described above, the subnetmanager 2450 is responsible for mapping a path between the end nodes insubnet 2400 via one or more linear forwarding tables. In addition, thesubnet manager can additionally be responsible for determining which endnodes are accessible via inter-subnet traffic—that is, data trafficoriginating from a remote subnet that is connected via a router, such asrouter 2426.

In accordance with an embodiment, the data attribute 2410 can comprise atable of entries (e.g., local identifiers) denoting which end node(according to its LID) is available for inter-sublet data traffic. Inaccordance with an embodiment, the subnet manager 2450 can populate/setthe data attribute 2410 after determining which end nodes are availablefor inter-subnet data traffic.

In accordance with an embodiment, for example, the subnet manager 2450can determine that end nodes 2430 and 2433 are available forinter-sublet data traffic, leaving end nodes 2431, 2432, 2434, and 2435not available for inter-subnet data traffic (for example, due tosecurity concerns). After such determination, the subnet manager 2450can set/populate the data attribute 2410, setting end nodes 2430 and2433 as available for inter-subnet data traffic, while the remaining endnodes are set as not available for inter-subnet data traffic.

In accordance with an embodiment, a firmware and embedded processor(e.g., the subnet management agent) of switch 2423 (which can comprisethe virtual router 2426), can be responsible for enforcing the allowedand disallowed data traffic to end nodes within subnet 2400. Forexample, if an inter-subnet data packet is inbound at router 2426, theSMA can, after determining the end node destination of the inter-subletdata packet, either allow the packet (if it is addressed to an allowedend node) or drop the packet (if it is addressed to a disallowed endnode). In accordance with an embodiment, the remote attribute 2110 cancomprise a remote physical node information attribute (also referred toherein as “RemPhysicalNodeInfo”), which can allow a subnet manager froma different subnet (not shown) to observe the physical connectivity ofthe subnet 2100.

In accordance with an embodiment, by ensuring that any incoming datapackets will be forwarded or dropped according to local subnet policyand configuration, the consistency of each local subnet is ensuredwhenever the local side of the external link is in active state.

FIG. 25 depicts a flow chart of a method for supporting SMA levelabstractions at router ports for enablement of data traffic in a highperformance computing environment, in accordance with an embodiment.

At step 2510, the method can provide, at one or more computers,including one or more microprocessors, a first subnet, the first subnetcomprising one or more switches, the one or more switches comprising atleast a leaf switch, wherein each of the one or more switches comprise aplurality of switch ports, a plurality of host channel adapters, eachhost channel adapter comprising at least one host channel adapter port,a plurality of end nodes, wherein each of the end nodes are associatedwith at least one host channel adapter of the plurality of host channeladapters, wherein each of the end nodes are associated with a localidentifier (LID) of a plurality of local identifiers, and a subnetmanager, the subnet manager running on one of the one or more switchesand the plurality of host channel adapters.

At step 2520, the method can configure a switch port of the plurality ofswitch ports on a switch of the one or more switches as a router port.

At step 2530, the method can logically connect the switch portconfigured as the router port to a virtual router.

At step 2540, the method can provide at the switch of the one or moreswitches that comprises the switch port of the plurality of switch portsconfigured as a router port a data attribute; wherein the data attributecomprises information about allowed and disallowed end nodes.

Features of the present invention can be implemented in, using, or withthe assistance of a computer program product which is a storage medium(media) or computer readable medium (media) having instructions storedthereon/in which can be used to program a processing system to performany of the features presented herein. The storage medium can include,but is not limited to, any type of disk including floppy disks, opticaldiscs, DVD, CD-ROMs, microdrive, and magneto-optical disks, ROMs, RAMs,EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or opticalcards, nanosystems (including molecular memory ICs), or any type ofmedia or device suitable for storing instructions and/or data.

Stored on any one of the machine readable medium (media), features ofthe present invention can be incorporated in software and/or firmwarefor controlling the hardware of a processing system, and for enabling aprocessing system to interact with other mechanism utilizing the resultsof the present invention. Such software or firmware may include, but isnot limited to, application code, device drivers, operating systems andexecution environments/containers.

Features of the invention may also be implemented in hardware using, forexample, hardware components such as application specific integratedcircuits (ASICs). Implementation of the hardware state machine so as toperform the functions described herein will be apparent to personsskilled in the relevant art.

Additionally, the present invention may be conveniently implementedusing one or more conventional general purpose or specialized digitalcomputer, computing device, machine, or microprocessor, including one ormore processors, memory and/or computer readable storage mediaprogrammed according to the teachings of the present disclosure.Appropriate software coding can readily be prepared by skilledprogrammers based on the teachings of the present disclosure, as will beapparent to those skilled in the software art.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample, and not limitation. It will be apparent to persons skilled inthe relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have often been arbitrarily defined herein for theconvenience of the description. Alternate boundaries can be defined solong as the specified functions and relationships thereof areappropriately performed. Any such alternate boundaries are thus withinthe scope and spirit of the invention.

The foregoing description of the present invention has been provided forthe purposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise forms disclosed. Thebreadth and scope of the present invention should not be limited by anyof the above-described exemplary embodiments. Many modifications andvariations will be apparent to the practitioner skilled in the art. Themodifications and variations include any relevant combination of thedisclosed features. The embodiments were chosen and described in orderto best explain the principles of the invention and its practicalapplication, thereby enabling others skilled in the art to understandthe invention for various embodiments and with various modificationsthat are suited to the particular use contemplated. It is intended thatthe scope of the invention be defined by the following claims and theirequivalents.

What is claimed is:
 1. A system for supporting SMA level abstractions atrouter ports for enablement of data traffic in a high performancecomputing environment, comprising: one or more microprocessors; a firstsubnet, the first subnet comprising a plurality switches of the firstsubnet, a plurality of end nodes of the first subnet, the plurality ofend nodes of the first subnet being interconnected via the plurality ofswitches of the first subnet, wherein each of the end nodes are assigneda local identifier (LID) of a plurality of local identifiers, and asubnet manager of the first subnet; wherein a switch port on a firstswitch of the plurality of switches of the first subnet ports isconfigured as a router port; wherein the switch port configured as therouter port is logically connected to a virtual router, wherein thevirtual router comprises two virtual router ports; wherein the subnetmanager configures an attribute at the first switch, the attributecomprising a set of plurality of end nodes to which inter-subnet datatraffic is disallowed; wherein upon receiving an inter-subnet datapacket at the first switch, the first switch determines, based upon theconfigured attribute, that a destination of the received inter-subnetdata packet is one of the set of the plurality of end nodes to whichinter-subnet data traffic is disallowed; and wherein upon suchdetermination, the first switch drops the inter-subnet data packet. 2.The system of claim 1, wherein the inter-subnet data packet is receivedfrom a second subnet, the second subnet being remote to the firstsubnet.
 3. The system of claim 2, wherein the first subnet isinterconnected to the second subnet via an intermediate subnet, theintermediate subnet comprising a first of the two virtual router portsof the virtual router.
 4. The system of claim 3, wherein the subnetmanager defines a logical end of the first subnet at the second of thetwo virtual router ports of the virtual router.
 5. The system of claim1, wherein the set of plurality of end nodes to which inter-subnet datatraffic is disallowed is defined by a table, the table comprising afirst set of LIDs, the first set of LIDs having been assigned to the setof plurality of end nodes to which inter-subnet data traffic isdisallowed.
 6. The system of claim 5, wherein the destination of thereceived inter-subnet data packet is determined based upon a destinationLID contained in a header of the received inter-subnet data packet. 7.The system of claim 6, wherein the destination LID of the receivedinter-subnet data packet is determined to belong to the first set ofLIDs.
 8. A method for supporting SMA level abstractions at router portsfor enablement of data traffic in a high performance computingenvironment, comprising: providing, at one or more computers eachincluding one or more microprocessors, a first subnet, the first subnetcomprising: a plurality switches of the first subnet, a plurality of endnodes of the first subnet, the plurality of end nodes of the firstsubnet being interconnected via the plurality of switches of the firstsubnet, wherein each of the end nodes are assigned a local identifier(LID) of a plurality of local identifiers, and a subnet manager of thefirst subnet; configuring a switch port on a first switch of theplurality of switches of the first subnet ports as a router port,wherein the switch port configured as the router port is logicallyconnected to a virtual router, wherein the virtual router comprises twovirtual router ports; configuring, by the subnet manager, an attributeat the first switch, the attribute comprising a set of plurality of endnodes to which inter-subnet data traffic is disallowed; upon receivingan inter-subnet data packet at the first switch, determining, by thefirst switch, based upon the configured attribute, that a destination ofthe received inter-subnet data packet is one of the set of the pluralityof end nodes to which inter-subnet data traffic is disallowed; and uponsuch determination, dropping, by the first switch, the inter-subnet datapacket.
 9. The method of claim 8, wherein the inter-subnet data packetis received from a second subnet, the second subnet being remote to thefirst subnet.
 10. The method of claim 9, wherein the first subnet isinterconnected to the second subnet via an intermediate subnet, theintermediate subnet comprising a first of the two virtual router portsof the virtual router.
 11. The method of claim 10, wherein the subnetmanager defines a logical end of the first subnet at the second of thetwo virtual router ports of the virtual router.
 12. The method of claim8, wherein the set of plurality of end nodes to which inter-subnet datatraffic is disallowed is defined by a table, the table comprising afirst set of LIDs, the first set of LIDs having been assigned to the setof plurality of end nodes to which inter-subnet data traffic isdisallowed.
 13. The method of claim 12, wherein the destination of thereceived inter-subnet data packet is determined based upon a destinationLID contained in a header of the received inter-subnet data packet. 14.The method of claim 13, wherein the destination LID of the receivedinter-subnet data packet is determined to belong to the first set ofLIDs.
 15. A non-transitory computer readable storage medium, includinginstructions stored thereon for supporting SMA level abstractions atrouter ports for enablement of data traffic in a high performancecomputing environment, which when read and executed by one or morecomputers cause the one or more computers to perform steps comprising:providing, at one or more computers each including one or moremicroprocessors, a first subnet, the first subnet comprising: aplurality switches of the first subnet, a plurality of end nodes of thefirst subnet, the plurality of end nodes of the first subnet beinginterconnected via the plurality of switches of the first subnet,wherein each of the end nodes are assigned a local identifier (LID) of aplurality of local identifiers, and a subnet manager of the firstsubnet; configuring a switch port on a first switch of the plurality ofswitches of the first subnet ports as a router port, wherein the switchport configured as the router port is logically connected to a virtualrouter, wherein the virtual router comprises two virtual router ports;configuring, by the subnet manager, an attribute at the first switch,the attribute comprising a set of plurality of end nodes to whichinter-subnet data traffic is disallowed; upon receiving an inter-subnetdata packet at the first switch, determining, by the first switch, basedupon the configured attribute, that a destination of the receivedinter-subnet data packet is one of the set of the plurality of end nodesto which inter-subnet data traffic is disallowed; and upon suchdetermination, dropping, by the first switch, the inter-subnet datapacket.
 16. The non-transitory computer readable storage medium of claim15, wherein the inter-subnet data packet is received from a secondsubnet, the second subnet being remote to the first subnet.
 17. Thenon-transitory computer readable storage medium of claim 16, wherein thefirst subnet is interconnected to the second subnet via an intermediatesubnet, the intermediate subnet comprising a first of the two virtualrouter ports of the virtual router.
 18. The non-transitory computerreadable storage medium of claim 17, wherein the subnet manager definesa logical end of the first subnet at the second of the two virtualrouter ports of the virtual router.
 19. The non-transitory computerreadable storage medium of claim 15, wherein the set of plurality of endnodes to which inter-subnet data traffic is disallowed is defined by atable, the table comprising a first set of LIDs, the first set of LIDshaving been assigned to the set of plurality of end nodes to whichinter-subnet data traffic is disallowed.
 20. The non-transitory computerreadable storage medium of claim 19, wherein the destination of thereceived inter-subnet data packet is determined based upon a destinationLID contained in a header of the received inter-subnet data packet; andwherein the destination LID of the received inter-subnet data packet isdetermined to belong to the first set of LI Ds.